My laboratory investigates the role of the nuclear receptors, CAR and PXR, in the regulation and induction of the sex-specific and sex-predominant drug-metabolizing P450s. Adverse drug reactions kill approximately 100,000 people each year, and induction of the drug metabolizing enzymes such as the P450s cause a number of these adverse drug reactions. Identification of the chemicals that induce P450s may help us predict potential adverse drug reactions, determine susceptible groups based on sex or occupation, and ultimately save lives. Nonylphenol (NP) is one of the most commonly found toxicants in the United States and Europe, and is considered a toxicant of concern because of its long half-life. Our data demonstrates that NP activates mouse and human CAR in vitro and in vivo, and in turn induces P450s involved in chemical detoxification. Preliminary data indicates that NP also activates rat, mouse, and human pregnane X-receptor (PXR) in vitro, but we have not examined the relevance of this interaction in vivo. Therefore, we will test whether NP activates PXR and induces P450s in vivo using wild-type, PXR-null, and humanized PXR (hPXR) mice. Humanized mice containing the human nuclear receptor in the place of the mouse nuclear receptor are essential in determining the significance of our observations to human health. In addition, we will determine CAR and PXR's role in maintaining gender differences, and inducing gender specific and gender predominant P450s in mice. Many of the xenobiotic-metabolizing P450s in the CYP2 and 3 families are gender predominant. We will (1) test whether CAR and PXR in part regulate or help maintain gender differences in P450 expression of several isoforms of the CYP2 and 3 families. We will (2) examine whether the toxicant NP, the CAR agonist TCPOBOP, and the PXR agonist Dexamethasone induce these P450 isoforms in a gender specific or gender predominant fashion in wild-type, CAR-null, and PXR-null mice. Furthermore, we will (3) test whether the gender predominant effects observed are pharmacologically relevant using zoxazolamine clearance and paralysis as a model for drug-toxicant interactions. Lastly, in order to determine the relevance of our in vivo observations to human health we will (4) determine if NP and other CAR/PXR activators such as dexamethasone and phenobarbital induce CYPs in a gender predominant fashion in primary human hepatocytes. We hypothesize that CAR and PXR play roles in the maintenance of the drug-metabolizing P450s and their gender predominance. Furthermore, we hypothesize that some of these P450s are induced in a gender predominant fashion by CAR and PXR agonists, which may cause pharmacologically relevant gender predominant effects.

Public Health Relevance

The purpose of this project is to further characterize the nuclear receptors CAR and PXR, as well as determine if they are involved in gender differences in P450 expression and adverse drug reactions.

National Institute of Health (NIH)
National Institute of Environmental Health Sciences (NIEHS)
Academic Research Enhancement Awards (AREA) (R15)
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Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Thompson, Claudia L
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Clemson University
Public Health & Prev Medicine
Schools of Earth Sciences/Natur
United States
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Kumar, Ramiya; Litoff, Elizabeth J; Boswell, W Tyler et al. (2018) High fat diet induced obesity is mitigated in Cyp3a-null female mice. Chem Biol Interact 289:129-140
Damiri, Basma; Baldwin, William S (2018) Cyp2b-Knockdown Mice Poorly Metabolize Corn Oil and Are Age-Dependent Obese. Lipids 53:871-884
Gissendanner, Chris R; Baldwin, William S; Schaaf, Marcel J M (2018) Non-Mammalian Nuclear Receptors: From Evolution to Human Disease. Nucl Receptor Res 5:
Schmidt, Allison M; Sengupta, Namrata; Saski, Christopher A et al. (2017) RNA sequencing indicates that atrazine induces multiple detoxification genes in Daphnia magna and this is a potential source of its mixture interactions with other chemicals. Chemosphere 189:699-708
Baldwin, William S; Boswell, W Tyler; Ginjupalli, Gautam et al. (2017) Annotation of the Nuclear Receptors in an Estuarine Fish species, Fundulus heteroclitus. Nucl Receptor Res 4:
Sengupta, Namrata; Reardon, Delaney C; Gerard, Patrick D et al. (2017) Exchange of polar lipids from adults to neonates in Daphnia magna: Perturbations in sphingomyelin allocation by dietary lipids and environmental toxicants. PLoS One 12:e0178131
Kumar, Ramiya; Mota, Linda C; Litoff, Elizabeth J et al. (2017) Compensatory changes in CYP expression in three different toxicology mouse models: CAR-null, Cyp3a-null, and Cyp2b9/10/13-null mice. PLoS One 12:e0174355
Sengupta, Namrata; Gerard, Patrick D; Baldwin, William S (2016) Perturbations in polar lipids, starvation survival and reproduction following exposure to unsaturated fatty acids or environmental toxicants in Daphnia magna. Chemosphere 144:2302-11
Sengupta, Namrata; Litoff, Elizabeth J; Baldwin, William S (2015) The HR96 activator, atrazine, reduces sensitivity of D. magna to triclosan and DHA. Chemosphere 128:299-306
Ginjupalli, Gautam K; Gerard, Patrick D; Baldwin, William S (2015) Arachidonic acid enhances reproduction in Daphnia magna and mitigates changes in sex ratios induced by pyriproxyfen. Environ Toxicol Chem 34:527-35

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